Hi,
i made a geomtry in gambit and exported it to fluent, while giving boundary conditions in fluent, it is showing me wall shadow for some of the walls. what does it mean? have i made some mistake in drawing geometry.

Hey Rage, with a name like that, you may not be starting out with enough patience for CFD

As for wall shadows, Fluent does that automatically for internal walls so it can distinguish between the shells attached to the volume element on one side vs the shell on the the volume element on the other side... It basically makes a copy of the internal wall and fixes the connections (or splits the internal wall if you would rather look at it that way). It is a good thing and you don't need to worry about it.

If you were planning to set a thermal boco or something on that internal wall, you will need to set it to both the wall and its shadow...